The broad objective of my research is to identify key genes that mediate fungal pathogenesis. The infectious fungus, Candida albicans, undergoes a serum-inducible morphologic transformation from unicellular to filamentous growth during the progression of invasive infection. The central method described in this proposal is to use filamentous growth mutants of Saccharomyces cerevisiae to unravel the regulation of filamentation in Candida. Functional complementation of Saccharomyces mutants defective in filamentation permits the cloning of cognate Candida genes that may be involved in Candida dimorphism. The ultimate objective of these studies is to identify potential targets for drugs effective in treating Candida infections. To identify such targets, cloned Candida genes predicted to be essential for filamentation will be disrupted in vivo to create defined mutants. Recently the PI identified on Candida gene, BUD1, that was found to be required for normal filamentous growth in response to serum. The Candida lambda bud1/lambda bud1 mutant and other mutant strains will be tested in mouse model of infection to identify essential virulence determinants. Any such determinants will be studied in biochemical detail. The PI is developing a direct genetic method for studying serum-induced Candida virulence functions. The PI has constructed a Candida expression vector that will make it possible to test dominant alleles of genes for their role in serum induction as well as to create an expression library that will permit the identification of regulators of filamentation directly in Candida. The PI's goal is to use the new techniques to initiate a strong basic research program in a poorly understood area of microbiology: he will carry this research program into a future academic career in Infectious Diseases.